Spitzer IRS observations of k+a galaxies: A link between PAH emission properties and AGN feedback?

TL;DR

This study uses Spitzer IRS spectroscopy to analyze PAH emission in post-starburst galaxies, revealing variations linked to starburst age and AGN activity, suggesting a connection between PAH properties and AGN feedback.

Contribution

The paper presents new mid-infrared spectral data on post-starburst galaxies, highlighting how PAH emission ratios evolve with starburst age and AGN activity, indicating a potential link between PAH properties and AGN feedback.

Findings

PAH emission line structures vary across post-starburst stages

PAH ratios correlate with time since starburst and AGN activity

Evidence suggests PAH evolution is related to AGN feedback processes

Abstract

We have performed IRS low resolution 5-12 micron spectroscopy on a sample of galaxies selected to be at 3 distinct post-starburst evolutionary stages based on their optical spectral indices. The resulting IRS spectra show distinctive PAH emission line structures at 6.2, 7.7, 8.6 and 11.3 micron and little silicate absorption, indicative of ongoing star formation. However the PAH inter-line ratios, in particular the 11.3/6.2 micron and 7.7/6.2 micron ratio, show large variations. These variations are found to correlate with both time since the most recent starburst and AGN activity. We speculate that the evolution observed in these PAH ratios is related to an increase in AGN activity with time since star burst.